1. Field of the Invention
This invention relates generally to processes and apparatus for disengaging bituminous material from crushed bituminous ores such as crushed tar sands and separating the disengaged bituminous material from the crushed ores.
2. Prior Art
The extraction of bituminous materials from ores containing the bituminous materials has been studied extensively for over half a century. The hot water process is presently being utilized commercially in Canada to recover bitumen from oil sands (sometimes also referred to as tar sands).
In the hot water process, oil sands is mixed with hot water having a slightly alkaline pH. The bitumen associated with the sand is thereby disengaged from the sand and dispersed in the resulting slurry. The slurry is treated to float a bituminous rich, aqueous layer from the slurry, with the bitumen then being recovered from the aqueous mixture.
Efficient separation of bitumen from the crushed mineral ore sands as well as from the aqueous mixture has been plagued with numerous problems, all of which result in reducing the degree of recovery of the bitumen from the mineral ore. A major difficulty experienced in the processing of the tar sand, or oil sand or oil shale has been the variability in the quality of the mineral ores which are being processed. In the commercial hot water process, the recovery of bitumen from oil sands is no greater than about 85% and the recovered bitumen will contain up to 30% inorganic contaminants. The feed ore must be of high grade quality or recoveries are reduced to even lower levels. The lower recoveries create additional problems in addition to the loss of bitumen. Low recoveries lead to substantial amounts of organic contaminants in the tailing streams. The organic contaminants promote formation of suspended solids in the aqueous streams in the form of an emulsion. The settling rates for the suspended solids in the emulsions is poor, and large settling ponds are required. The settling ponds create environmental problems, and the ponds can also cover large areas which could otherwise be used as valuable resource land.
Quality of the mineral ore varies greatly from one location to another and even at different depths in the same deposit. As a general rule, the low grade or.RTM.s have a rather high content of finely divided clay or siliceous material commonly known in the trade as fines. In addition, the low grade ores yield bitumen having high viscosity, and, of course, the bitumen loading or content is low. All of these factors tend to increase the difficulty which is incurred when the low grade ores are processed. Because of the many problems associated with processing the low grade ores, it has generally been thought that the low grade ores were not worth processing. However, there are vast reserves of oil tied up in the low grade ores, and it would be highly desirable and advantageous to be able to economically recover these oil reserves. Of course, any improvement which would aid in recovering bitumen from low grade ores would likely result in improved recoveries for the higher grade ores also.